To prevent water pollution and further the goals of the Clean Water Act, regulations and enforcement actions have historically focused on the output of wastewater treatment facilities. However, in recent years, the technology for treating wastewater has largely matured to the point that treatment facilities are decreasingly the source of significant water pollution. To further eliminate potential water pollution, the United States Environmental Protection Agency, municipalities and sanitary sewer system authorities have recently refocused their attention and resources on the network of pipes that transports wastewater to the treatment facility.
These piping networks may be constructed as a combined wastewater and storm water system, or dedicated exclusively to the transport of wastewater. In either case, untreated wastewater can overflow from the system into the environment. For the health of the community and environment, and to remain in compliance with the law, a sanitary sewer system authority must prevent such overflows. To retain a permit to operate a sanitary sewer system, an authority must “take all reasonable steps to minimize or prevent any discharge . . . which has a reasonable likelihood of adversely affecting human health or the environment.” 40 CFR 122.41(d).
Sanitary system overflows, or SSO's, can be caused by a number of factors. The primary cause of overflows is restrictions and blockages in the sewer system, most often caused by the accumulation of debris, roots and/or grease in a sewer pipe. Although less common, underground pipes also may settle, rupture or deteriorate, especially in older collection systems. In wet weather conditions, storm water runoff may infiltrate a dedicated sanitary sewer system, or overwhelm the capacity of a combined sanitary sewer and storm water system, and cause the sanitary system to overflow. Because an SSO may result in untreated sewage being released into the environment or backing up into residential basements, municipalities and sanitary sewer system authorities seek technology and methods to identify actual and potential causes for an SSO.
In the past, municipalities and sanitary system authorities have addressed actual and potential sanitary sewer system overflows in a number of ways. Many authorities have simply built additional or redundant capacity into their piping system to prevent overflows. Studies have shown, however, that restrictions and blockages are the primary cause of overflows, not lack of capacity in the system. Thus, simply adding additional capacity leads to piping systems that are underutilized and more expensive than necessary to serve the sanitary needs of the community.
Some larger authorities have employed complex and expensive evaluation methods to identify potential causes of SSO's. These methods often include the use of expensive devices for monitoring flow at different points in the system and the employment of personnel and/or consultants to collect and analyze data from the flow monitoring devices. The data is often analyzed with proprietary software by paid consultants.
These techniques, associated devices and software, however, are often beyond the financial capacity and skill set of small and medium sized sanitary system authorities. Also, because of the cost and complexity of these evaluation methods, a complete review of the entire sanitary system is typically not performed. Thus, although general problem areas in the system may be identified, specific pipe restrictions and blockages may be missed.
In addition, due to the cost of employing data collection personnel and consultants, the review and analysis of most sanitary sewer systems is typically short lived, and usually only performed in response to a specific problem or overflow. Prior art evaluation techniques are typically project-based, specific to a particular problem and not designed for ongoing assessment of the collection network. The resultant data is typically not incorporated into the ongoing operation and maintenance procedures of the authority, and is therefore not helpful in identifying and solving future problems in the system.
In addition, because the evaluation of sanitary sewer systems has historically been project-based and in response to a specific problem or overflow, little attention has been paid to the ongoing maintenance and upkeep of the system. However, sewer system assets that are not regularly maintained will deteriorate faster, leading to higher replacement and emergency response costs. When a sewer system is regularly maintained, its lifetime can be increased and maintenance costs distributed over the lifetime of the system. Thus, a regular evaluation and maintenance program will save money in the long run, avoid unexpected and unplanned for costs and safeguard against the health risks associated with SSO's.
Accordingly, an object of the present invention is to provide an evaluation method for identifying potential causes of sanitary system overflows including restrictions and blockages in the piping system, ruptured or deteriorated pipes and sources of storm water inflow and infiltration into the system.
A further object of the present invention is to provide an evaluation method that specifically identifies problem points in the collection network and avoids the need for building additional or redundant capacity in the system.
Yet another object of the present invention is to provide an evaluation method that is inexpensive to administer and easy to understand.
An additional object of the present invention is to provide an evaluation method that can be used to evaluate the entire sanitary sewer system and that can be easily performed on an ongoing basis.
Finally, an object of the present invention is to provide an evaluation method that can be incorporated as part of an ongoing sewer system maintenance and upkeep program to prolong the life of the system and avoid unexpected and unplanned for costs.